The present invention relates to an inductive device using a magnetic induction phenomenon of a coil, a transformer, a common mode choke coil, etc. and a method for producing the inductive device. Particularly it relates to a structure of an inductive device permitting mass production of high-performance narrow-tolerance devices and a method for producing the inductive device.
The method for producing this type inductive device has been heretofore roughly classified into the following processes.
(1) Winding Process
This is a most general process in which a wire is wound on a magnetic or non-magnetic core.
(2) Building-up Process
This is a process described in JP-A-2002-134321. In this process, electrically insulating boards having coil conductors provided to form part of a helical coil and electrically insulating layers are laminated alternately to form a helical coil.
The processes have the following problems respectively.
(1) Winding Process
a: Performance of a coil is good but tolerance has an inconvenient tendency toward increase.
b: Poor mass production efficiency causes increase in cost because of necessity of winding operation.
(2) Building-up Process
a: When the number of turns increases, tolerance becomes high because the number of laminated layers increases.
b: When the number of turns increases, mass production efficiency is lowered because the number of laminated layers increases.